Turbo charged engines utilize a Charge Air Cooler (CAC) to cool compressed air from the turbocharger, before it enters the engine. Ambient air from outside the vehicle travels across the CAC to cool intake air passing through the inside of the CAC. Condensate may form in the CAC when the ambient air temperature decreases, or during humid or rainy weather conditions, where the intake air is cooled below the water dew point. When the intake air includes recirculated exhaust gasses, the condensate can become acidic and corrode the CAC housing. The corrosion can lead to leaks between the air charge, the atmosphere, and possibly the coolant in the case of water-to-air coolers. Condensate may collect at the bottom of the CAC, and then be drawn into the engine at once during acceleration increasing the chance of engine misfire.
Other attempts to address condensate formation include restricting intake air travelling through the CAC or restricting ambient air flow to the CAC. One example approach is shown by Craig et al. in U.S. Pat. No. 6,408,831. Therein, the intake air temperature is controlled by an ambient air flow restriction system and an intake air flow restriction system. A controller defines the position of these restriction devices and is connected to a plurality of sensors which measure different variables such as ambient air and intake air temperatures.
However, the inventors herein have recognized potential issues with such systems. Specifically, the above control of restriction devices in response to intake or ambient air temperature may reduce the overall level of condensate, while potentially increasing the concentration of acid in the condensate that does form. Maintaining temperatures at a certain level such that condensate formation is low may result in sustaining a flow restriction for a period of time. This keeps the CAC effectiveness at one level, causing the dew point to hover at one location in the CAC. This may result in an increased acid concentration at one location, actually creating a higher corrosion risk. This is because the corrosion risk is most severe at the location in the CAC where the charge air temperature drops below the dew point and water begins to condense, creating the highly concentrated water and acid solution, especially if the level of condensate it kept low.
In one example, the issues described above may be addressed by a method for controlling vehicle grille shutters, comprising: adjusting grille shutter opening in response to a condensate location in a charge air cooler remaining within a positional range for greater than a threshold duration. The grille shutters may be adjusted to move the condensate location toward an inlet of the charge air cooler (e.g., increase shutter opening) during a first set of conditions, and may be adjusted to move the condensate location toward an outlet (e.g., decrease shutter opening) during a second, different, set of conditions. In this way, by moving the location of the condensate formation, e.g., back and forth, if the location becomes stagnant, it is possible to reduce corrosion risk at any given location from the inlet to the outlet of the charge air cooler, as one example.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.